Lock for stitch adjusting mechanisms



' Feb; 1 1944.

G. MINKOWITZ LOOK FOR STITCH ADJUSTING MECHANISM Filed Jan. 26, 1940 lNVEN TOR I eorje Mn C Z BY 1 ATTORNEY.

Patented Feb. 1, 1944 LOCK FOR STITCHADJUSTING MECHANISMS GeorgeMinkc'witz, New York, -N." Y. j Application January 26, 1940, SerialNo; 315,643 3 Olaims. (01. 112-210) This invention relates-an-anattachment for sewing machines to prevent unauthorizedalteration in the stitch adjustment mechanism.

Sewing machine operators are usually employed on piece work, that is to say they are paid according to the number of articles completed. At the same time there are certain-standards set for the various types of this work and one of the most important requirements in stitchingis' to include in each article construction a certain number of stitches per inch. Practically all sewing machines are equipped with stitch adjusting mechanism,-whereby by adjustment ofthe feed bar any desirable number of stitches may beprovided in a single article. When piece work is contracted for, it is stipulated that-each inch of stitching must embody a certain number of stitches and the feed bar adjustments aresetaccordingly. Dishonest operators of .machines have found tion and their income by reducing-the number of stitches per inch and consequently at a convenient time they purposely change the adjustment of their machines to produce fewer stitches. The result is that an article is made more quickly, but its quality is poor and when the dishonest practice is discovered by the party for whom the work has been done, the entire contract may be cancelled, causing considerable loss in money and materials.

With the foregoing in mind, it is the purpose of the present invention to provide a lock for the stitch adjusting mechanism of a sewing machine whereby the adjusting mechanism can be properly set and locked by an authorized party and an operator of the machine is unable to make any changes in the setting to alter the predetermined number of stitches per inch for which the device has been set and locked.

I accomplish this object by means of a device, which is attachable to an ordinary sewing machine, and which is locked by means of a key not accessible to the operator of the machine.

One embodiment of my invention is described in the following specification, set forth in the appended claims and illustratively exemplified in the accompanying drawing in which:

Figure 1 is a fragmental perspective view of a sewing machine with the bed broken away and showing the needle and portions of the usual feed adjusting mechanism together with the locking device forming the subject matter of the present invention.

Fig. 2 is a substantially longitudinal sectional view of the locking device;

that-they can increase their produc-- Fig. 3 is:a rear elevational viewof the locking v 1 device; and

Fig. 4 is an elevational view'of a' portion of the front of the locking device.

Referring to the' drawing, Ill denotes the machine bed and II the upright .standardfor the overhanging arm supporting the' needle I2. The machine-bed I Il'is :provided .with aplate 13; beneath the needle I2and'whic'h plate' is' provided with feed dogslots' I4 anda-needle aperture I5.

As-in the usual practice, a feed dogis given feed movements throughslots M'by' means of: a feed advance rockshaft 20which' receives rocking movementxby ime'ans of'ia'n arm-22 actuated by apitman r0d 23 extendingf upwardly within the standard I I to theusu'al arm supportedoperciting mechanism. F Further, as in usual practice a feed adjusting arm '21 is operative through cooperating means between same and f the 'rod for varying the vertical component of'movement of the rod and with" correspondingadjustme'nt of the feed dog. The arm 27 is provided with a forwardly extending threaded-"stem 28 of a screw 29 which passes to the outside of the standard through an arcuate slot 30 to afford outside access to the adjustment mechanism. The parts described thus far are those usually provided in a sewing machine of this character, whereby any one may effect the necessary adjustment to change the movement of the feed bar and the range of stitches per inch.

According to the present invention the screw 29 is properly adjusted for the stitch arrangement and is then locked against further adjustment. The attachment devised for this purpose, comprises a base plate 3 l which is mounted upon the upper surface of the machine bed II] at the front corner thereof adjacent the standard II. One end of the base plate 3| is located directly beneath the set screw 29 and arcuate slot 33 and is provided with a groove 32 projecting outwardly from the wall of the standard I I to accommodate the short lateral arm 33 of an L-shaped standard 34, the other arm 35 thereof projecting perpendicularly towards the screw 29. The rear face of the upright arm 35 is grooved longitudinally thereof from its upper end to a point above the angle of the standard 34, where it tapers off to the rear surface. The bottom wall of the groove 36 is provided with a longitudinal slot 31.

Slidably mounted in the groove 36 is a slide bar 38, which forms an extensible portion of the standard 34, and which has a yoke 39 at its upper end with a pivot pin 40 between the arms thereof. A link 4| is reduced at one end and pivotally mounted on the pin 40 in the yoke 39 and its upper free end is provided with an opening 42 which aligns itself with the axis of the arcuate slot 30 and receives the stem 28 of the set screw 29. The screw 29 is provided with a knurled head 43 to enable the screw to be released or tightened on the link 4 I When proper adjustment of the screw has been made and the relative extension of the bar 38 automatically effected, the latter and the upright arm 35 of the standard 34 are locked together by means of a clamping device, see Fig. 2, comprising a screw 44 projecting forwardly through a threaded opening 45 in the lower end of the bar 38, and then through the slot 31 to receive a frustro-conical nut 46. The rear face 7 of the nut 46 is provided with a hub 41 abutting the surface of the arm 35 on opposite sides of the Having described my invention and the manner in which the same operates what I claim and desire to secure by Letters Patent is:

1. In a sewing machine having means for changing the number of stitches per inch, the combination of an angularly adjustable arm connected to the stitch changing means and a looking attachment for the machine mounted on the latter and having an extensible arm projecting upwardly over the path of movement of the angularly adjustable arm, the free end of the extensible arm comprising a pivotally mounted link provided with an opening to receive the angularlyadjustable arm, and a screw clamp for lockslot 31 and being disposed in an opening 43 ofa flanged washer 49, the flange 56 thereof pro-- -jecting outwardly from the base of the nut 46 to provide a V-shaped circular groove between the .conical wall of the nut and inner periphery of the flange. This construction is designed to prevent a tool from being used to engage the outer tapering periphery of the nut and thus release it. The bottom wall of the washer is of less thickness than that of the hub 41 which enables the washer to turn freely upon the nut. I

The nut 46 is actually released or tightened on the screw 44 by means of a removablekey 5| having spanning pins 52 which fit spaced openings 53 in the front face of the nut.

In operation, the proper adjustment of the stitch mechanism is eifected by changing the position of the screw 29- in the slot 30 .and tightening the head 43. The extension bar 38 is now in position to be locked to the standard arm 35. The nut 46 is tightened, over the screw 44, to clamp the bar 38 and arm 35 tightly together. The key 5| used to tighten the nut 46 is then removed and the machine is ready to be used by the operator who, without a key, is unable to change the adjustment and alter the stitches.

ing the extensible arm against unauthorized longitudinal adjustment.

2. A locking attachment for stitch changing mechanism of a sewing machine, comprising a standard mounted upon the machine, a slide bar for the standard having a link connection with the stitch changing mechanism, and a key operated clamp to lock the slide bar in adjusted position on the standard, comprising a screw carried by the slide bar and projecting through a slot in the standard, a flanged washer on the outer face of the standard axially aligned with the screw, and a turning element on the screw and loosely supporting the washer, said element being disposed within the flange of the washer and having a hub on its inner face to project through an opening in the washer and engage the standard and having spaced openings on its outer face to receive the spanning pins of a key for the purpose of turning the element to tighten or release the clamp.

3. A locking attachment for stitch changing mechanism of a sewing machine, as claimed in claim 2, in which the turning element is of frustro-conical shape, the base and adjacent portion of the tapered periphery thereof being arranged within the washer and closely adjacent the inneriperiphery thereof to prevent a hold being obtained upon the side of the element.

GEORGE MINKOWITZ. 

